1. Field of the Invention
This invention relates to a flat panel display device such as a liquid crystal display device and a manufacturing method thereof.
2. Description of the Prior Art
A conventional liquid crystal display module production method will be described with reference to drawings of production process shown in FIG. 10.
After a liquid crystal cell 102 is produced, anisotropic conductive film (hereinafter referred to as ACF) is bonded along an edge portion of the liquid crystal cell 102.
This bonded ACF is heated by a heating means 103 and a tape carrier package (hereinafter referred to as TCP) is temporarily press-fit.
After that, this TCP 104 is heated again from up so as to press-fit the TCP 104 to the liquid crystal cell 102.
Next, the ACF 112 is bonded to a printed circuit board (hereinafter referred to as PCB) 106.
Finally, the positions of the plurality of the TCPs 104 attached to the liquid crystal cell 102 are matched with that of the PCB 106 to be mounted thereon and then the PCB 106 and the TCPs 104 are bonded together with the ACF 112 and fixed.
The above mentioned bonding process for bonding the ACF 112 to the PCB 106 has a following first problem.
On a back side of the PCB 106 is already formed a wiring structure 115 such as a copper (Cu) wiring pattern and IVH (interstitial via hole) or a printed pattern by silk screen for indicating PCB serial number. Therefore, a quite number of unevenness are formed on the back side of the PCB 106.
However, the bonding of the ACF 112 is carried out by hands of a worker by visually checking a position of the land group so that the ACF 112 covers a region confirmed by him.
Therefore, the conventional art has the following problems.
(1) First, it is very difficult to secure a bonding position accuracy for the ACF 112, and if it is intended to improve the position accuracy, even a skilled worker needs a sufficient working time. To reduce a working load, it can be considered to ensure a large dimensional margin. However, this does not only lead to increase of production cost, but also conflicts with a demand for narrowing of the frame edge.
(2) As shown in FIG. 12, upon thermo compression bonding, a back side of a terminal connecting portion to which a heat tool 120 is to be applied is covered partly with a printed pattern having a quite thickness such as a wiring pattern 115. Thus, sometimes, a pressing force by the heat tool 120 is not applied equally or sometimes heating is not carried out equally, so that there is a fear that a connection failure may occur in part of the terminals. If the connecting reliability is intended to be secured sufficiently, a time and pressure for thermo compression bonding need to be set to be larger than values originally necessary. Thus, a necessary process load will be increased.
In the process for matching the positions of the TCP 104 and PCB 106, the following second problem exists.
FIG. 13 is a further detailed explanatory view as viewing a case in which the position matching between the TCP 104 and PCB 106 is carried out, through a plan. That is, this figure shows a condition that the position of the TCP 104 fixed to the edge of the liquid crystal 102 is matched with that of the lands 110 of the PCB 106.
If the position of the TCP 104 is matched with that of the PCB 106 in the above production process, as shown in FIG. 13, the liquid crystal cell 102 is fixed to a first jig 114 and on the other hand, the PCB 106 is installed on a second jig 116, and the positions of the jigs 114, 116 are matched. Then, the positions of the TCP 104 and PCB 106 are matched with each other.
However, if the above described method for matching the positions of the TCP 104 and PCB 106 is applied, the limit of the gap e between leads 108 of the TCP 104 is 0.5 mm and the position matching with a finer pitch cannot be carried out.
Accordingly, the present invention has been achieved in views of the above problems and therefore, a first object of the invention is to provide a flat panel display device capable of improving a position accuracy when an ACF is provided so as to obtain electrical and mechanical connections. Further, a second object of the invention is to provide a manufacturing method of a flat panel display device enabling to match the position of a flexible wiring board having leads having a finer pitch with that of a land of a printed circuit board.
To achieve the above object, according to a first aspect of the present invention, there is provided a flat panel display device comprising: a display panel in which a plurality of display picture elements are disposed; a first wiring board one end of which is connected electrically to the display panel and provided with a first terminal group at the other end thereof; and a second wiring board provided with a second terminal group corresponding to the first terminal group at a main surface thereof, electrically connected to the first terminal group through an anisotropic conductive film, for outputting a control signal to the display panel, the second wiring board having position indicating marks for indicating a disposition position of the anisotropic conductive film.
According to a second aspect of the present invention, there is provided a manufacturing method of a flat panel display device comprising: a display panel in which a plurality of display picture elements are disposed; a flexible electrode substrate having a plurality of leads to be connected electrically to the display panel; and a wiring board having a plurality of lands corresponding to the leads of the flexible electrode substrates and for supplying a control signal to the display panel, the manufacturing method comprising the steps of: disposing the leads of the flexible electrode substrate and the lands of the wiring board such that they oppose; irradiating with light having a light axis inclined at an angle smaller than 90xc2x0 relative to an axis line of the lead; and detecting relative positions of the leads and the lands irradiated by the light and matching positions thereof by a picture detecting portion disposed above the leads.
According to a third aspect of the present invention, there is provided a flat panel display device wherein a connecting region at an end of a lead of a flexible substrate mounted on a display panel is connected to lands on a top surface of a wiring board via an anisotropic conductive film, the lands of the wiring board being longer than the connecting region of the lead of the flexible substrate.
According to a fourth aspect of the present invention, there is provided a flat panel display device wherein a connecting region at an end of a lead of a flexible substrate mounted on a display panel is connected to lands on a top surface of a wiring board via an anisotropic conductive film, the lands of the wiring board being longer than a width of the anisotropic conductive film.
According to a fifth aspect of the present invention, there is provided a manufacturing method of a flat panel display device comprising: a display panel; a flexible electrode substrate having a plurality of leads to be electrically connected to the display panel; and a wiring board having a plurality of lands corresponding to the lead of the flexible substrate and for supplying a control signal to the display panel, the manufacturing method comprising the steps of: disposing the anisotropic conductive film on the wiring board following position indicating marks provided on the wiring board to indicate a wiring position of the anisotropic conductive film;
disposing the leads of the flexible substrate and the lands of the wiring board such that they oppose; irradiating with light having a light axis inclined at an angle smaller than 90xc2x0 relative to an axis line of the lead; detecting relative positions of the leads and the lands irradiated by the light and matching positions thereof by a picture detecting portion disposed above the leads; and fixing the flexible substrate and the wiring board with the anisotropic conductive film.
In the flat panel display device according to the first aspect of the invention, the position accuracy for providing the anisotropic conductive film can be improved and the working load can be reduced.
According to the manufacturing method of the flat panel display device of the second aspect of the invention, by irradiating light from a light source located substantially above an axis line of the lead of a flexible substrate, the shadow of the lead located below a thin film member appears on a top surface so that the position of the lead becomes clear. Then, the position of the lead whose position is made clear is matched with that of the land of the PCB and both the members are fixed with the anisotropic conductive film. In this case, because the light source is located substantially just above the axis of the lead, even if any shadow is generated by light from the light source, the size of the shadow is substantially the same as the width of the lead, therefore, an accurate positioning can be achieved.
In the flat panel display device according to the third aspect of the invention, if the flexible substrate has light transmitting characteristic, the shadow of the lead appears more clearly so that the positioning thereof is facilitated.
In the flat panel display device of the fourth aspect of the invention, by extending the lands of the PCB relative to the connecting region of the lead of the flexible substrate, the lands protrude from the lead portion when the position matching is carried out, so that the position of the land is made clear thereby facilitating the position matching thereof.
In the flat panel display device of the fifth aspect, because the lands of the PCB protrudes long from the ACF, even if the flexible substrate is superimposed on the ACF, the position matching thereof can be carried out easily because the lands protrudes further.